FIG. 1 is a schematic illustrating a system structure of a system architecture evolution (SAE). Wherein:
user equipment (UE) 101 is a terminal device for receiving data. Evolved universal terrestrial radio access network (E-UTRAN) 102 is a wireless access network which includes eNodeB/NodeB for providing UEs with interfaces for accessing the wireless network. Mobility management entity (MME) 103 is for managing mobility context, session context and security information of UEs. Serving gateway (SGW) 104 is mainly for providing user plain functions. MME 103 and SGW 104 may reside in the same physical entity. Packet data network (PDN) gateway (PGW) is for implementing functions including accounting, lawful interception and so on, and may reside in the same physical entity with SGW 104. Policy and charging rule functions (PCRF) 106 provides Quality of Service (QoS) policies and charging rules. Serving GPRS support node (SGSN) 108 is a network node device providing routing for data transmission in the Universal Mobile Telecommunications System (UMTS). Home Subscriber Server (HSS) 109 is a home sub system of UEs, is for maintaining user information including current location, the address of the serving node, user security information, packet data context of a UE.
Minimization of drive tests (MDT) is measurement information transmitted in the control plain for reducing workload of manual tests. MDT measurements include real time measurements and non-real time measurements. Configuration of the measurements is configured in an access network controlling system (E-UTRAN or UTRAN) by a network management system, and is sent by the access network controlling system to the UEs via an RRC message. The UE sends its MDT measurement results to the E-UTRAN/UTRAN. A measurement report may include location information and time information. The E-UTRAN/UTRAN sends the measurement results to an MDT entity in the core network.
MDT can be divided into management-based MDT and signaling-based MDT according to the manner in which the MDT is initiated. The management-based MDT refers to an MDT-activated message received by the E-UTRAN/UTRAN from a management entity, while the signaling-based MDT refers to an MDT-activated message received by the E-UTRAN/UTRAN from an MME.
FIG. 2 is a schematic illustrating a structure of a management-based MDT. In FIG. 2, 201 is an element management (EM) for sending a trace activation request to network element 202. The trace activation request may include MDT configuration information and a trace reference (TR).
Network element 202 selects a UE for performing MDT, allocates a trace record session reference (TRSR), and sends a message which includes MDT configuration information, the TR and the TRSR to UE 203.
UE 203 performs MDT according to the MDT configuration information, and sends measurement results to the network element via an MDT report when a reporting condition is satisfied.
The network element sends a message which includes the TR and the TRSR to the MME. The MME obtains the international mobile subscriber identification (IMSI) or the international mobile equipment identity and software version (IMEISV) of the UE, and sends the IMSI/IMEISV to a trace collection entity (TCE).
Network element 202 stores an MDT record, and sends the MDT record, the TR and the TRSR to TCE 204 according to a pre-defined policy.
The TCE identifies the UE of the MDT record based on information sent by the MME and information sent by the network element.
Initiation of the MDT makes use of a conventional Trace process, and is a special one of Trace functions. Taking the signaling process in the E-UTRAN as an example, FIG. 3 shows a flowchart of a signaling process of initiating a management-based MDT according to the prior art. In block 301, an MME sends an initial context establishing request which includes a user consent to the eNB in this block if a UE has established an RRC connection with an eNB in a conventional RRC establishing process before this block is performed; or the MME sends a handover request which includes a user consent to the eNB in this block if the UE has been handed over from a serving eNB to a target eNB before this block is performed. Subsequent handover process is the same with the conventional handover process, and will not be described further herein. The user consent indicates whether the UE is available for performing the MDT. The user consent belongs to subscription information of the UE, is stored in the HSS and is sent to the MME. After receiving the initial context establishing request or the handover request from the MME, the eNB stores the user consent if the request includes the user consent, and takes the user consent into consideration when selecting a UE for performing MDT. In block 302, the EM sends a Trace activation request to the eNB. The EM is a management element, and the Trace activation request may include MDT configuration information. The MDT configuration information may mainly include: MDT location selection condition, reporting scheme configuration, TR, the IP address of the TCE, a work mode and MDT data anonymity information and so on.
The work mode may be configured to be one of the following four modes: Immediate MDT only, Logged MDT only, Trace only and Immediate MDT and Trace. Wherein:
Immediate MDT only is a real time-type MDT, indicating the UE should perform MDT in a connection mode. Logged MDT only is a log-type MDT, indicating the UE obtains MDT configuration under the connection mode, performs MDT in the idle mode, and reports MDT measurement results when returning to the connection mode. Trace only indicates only tracing is performed, and is not a type of MDT. Immediate MDT and Trace refers to both real time MDT measurements and trace measurements are to be performed.
The MDT location selection condition defines locations of UEs which can be selected for performing MDT. The MDT location selection condition may be configured as a coverage area of a cell, or a coverage area of a Type Allocation Code (TAC), or a whole PLMN. UEs within the location range can be selected as UEs performing the MDT. A TR uniquely identifies an MDT process. In one MDT process, an eNB may select multiple users to perform the MDT.
In block 303, the eNB firstly selects UEs for performing the MDT after receiving the Trace activation request. When selecting UEs, the eNB needs to take the user consent sent by the MME and the location selection condition in the MDT configuration information into consideration. If the UE is not consent to performing MDT or if the UE does not meet the location selection condition, the UE can not be selected for performing MDT. After the UE is selected, the eNB allocates a TRSR to the UE, and sends the MDT configuration information to the UE. The configuration information may include: a location selection condition, a reporting scheme configuration, the TR, the TRSR, and an identifier of the IP address of the TCE. In block 304, after receiving the MDT configuration information, the UE starts MDT functions according to the MDT configuration.
In block 305, after performing the MDT, the UE sends a MDT measurement report to the eNB. In block 306, after receiving the MDT measurement report from the UE, the eNB obtains the TR, the TRSR, the identifier of the IP address of the TCE and the measurement results from the measurement report, obtains the IP address of the TCE based on the identifier of the IP address of the TCE, sends a cell traffic trace message to the MME, wherein the relation which associates the IP address of the TCE with the identifier of the IP address is stored in the eNB in advance, the cell traffic trace message includes the TR, the TRSR, a cell ID, and an S1 AP Id allocated for the UE by the eNB and the MME, and the IP address of the TCE. In block 307, after receiving the cell traffic trace message, the MME obtains context information of the UE, obtains the IMSI/IMEISV information, and sends to the TCE a message which includes the IMSI/IMEISV of the UE, the TR and the TRSR. In block 308, the eNB reports collected MDT measurements to the TCE.
In block 302, the MDT configuration information in the Trace activation request sent by the EM to the eNB may further include MDT data anonymity information. The MDT data anonymity information may be configured to be two anonymity levels, i.e., TAC-level anonymity and full anonymity. When TAC-level anonymity is configured, the MME is required not to send the IMSI/IMEISV to the TCE, but send the TAC information in the IMEI to the TCE instead. When full anonymity is configured, the eNB does not send the cell traffic trace to the MME, and the MME does not send any identification of the UE to the TCE.